#include<iostream>
using namespace std;
#define pi 3.141592653

class Circle
{
public:
    Circle(int);  //initial function
    double Area(void);
private:
    int radius;
};
Circle::Circle(int r){
    radius = r;
}
double Circle::Area(void){
    return radius*radius*pi;
}

int main(void)
{
    Circle cir1(10);
    cout<<"Circle1's area: "<<cir1.Area()<<endl;
    Circle cir2(1);
    cout<<"Circle2's area: "<<cir2.Area()<<endl;

    return 0;
}